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Topic Review (Newest First)

02-23-2013 05:43 PM

smith9300

Thanks a to Mr p that is a very good help but yea I have thought about getting that cam insTed and I prb will before its all over with

02-23-2013 04:44 PM

jtz55

Quote:

Originally Posted by vinniekq2

using equal or better parts Im sure its 100% Thanks for the answer

no problem Vinnie I should of stated that we were a little more of a complete rebuild than just a intake and a cam .with the kb pistons and 64 cc vortec heads the scr was at 9.5 .

don't know if the OP is upgrading the rods and pistons .the comp.on those stock 400's were about 8.5 with a dismal quench. heads were junk and a 2barrel carb,not exactly a big HP combo.think I recall f-bird saying he had a high HP version out of a 70 something chevy but cant remember what.

02-23-2013 04:07 PM

Mr. P-Body

I use Performance Trends Engine Analyzer "Pro". It's a decent simulator. We use it primarily to plot power curves and anticipate results from changes. As for the "peak" numbers, I've seen it anywhere from dead-on to 15% "high" based on engines that went to real dynos. So take the numbers with a "grain of salt". I'd be willing to say they're within 10%, reliably.

When I saw the XE256H cam listed, I realized the "guessing" going on was based on smaller engines or larger cams. I've used this cam in both small blocks and Pontiacs extensively. The 400 Chevy "likes" cams more like the Pontiac than the 350, IMO. This cam will have pretty much a "dead smooth" idle in a 400. Stock converter is fine.

I "assumed" Performer, as he mentions Edelbrock, and RPM isn't appropriate for this cam. The 650 carb IS a bit small, I agree. But with this cam, it works to the "curve" the 400 has. I also "assumed" 1 5/8" headers, "open".

Following are the numbers generated, using the real data for all the parts, 93 octane gasoline, 165 deg. test temp, (note the program assumes "perfect" air and timing).

Based on all this, I'd say the torque numbers are a bit high, but HP numbers are a bit low. Having used that cam in several 400 Pontiacs with stock heads, the curves fall "in line" with an engine of this displacement. The Pontiac will make a little more torque and a little less HP, but the ranges are the same. For those unaware, the Pontiac and Chevy 400s are close enough in bore/stroke and volumetric efficiency at these speeds, the data is "good" for either. The longer rod and taller deck makes the Pontiac more of a "torque" engine, and the shorter rod and good heads make the Chevy more of a "HP" engine.

I would say this combination would be dynamite in a heavier car for "sporting use", not racing or serious performance. It might get pretty decent gas mileage, too. Even though I'm well known as a Pontiac "bigot", I'm not stupid about Chevys... (:- The 400 has SERIOUS potential when properly built.

If you want to "move the power up" just a bit, and still enjoy GOOD low-end, use XE262H instead. The 750 carb with that cam would really wake it up. 1 3/4" headers would be called for here.

Sounds like a nice street engine, either way!

Jim

02-23-2013 01:54 PM

vinniekq2

varified

Quote:

Originally Posted by jtz55

Vinnie its the same motor chp built a few years back called the impersonator .they claimed 425hp and 525 ft lbs .u can look it up just do a search on it .was june 2003.anyway I built mine to spec just a little bigger carb(mines a 800 )I know they inflate the numbers a little but guys in the know that have been in my car say that its pretty close so I would have to say alittle of verified and alittle estimated.

using equal or better parts Im sure its 100% Thanks for the answer

02-23-2013 11:28 AM

jtz55

Vinnie its the same motor chp built a few years back called the impersonator .they claimed 425hp and 525 ft lbs .u can look it up just do a search on it .was june 2003.anyway I built mine to spec just a little bigger carb(mines a 800 )I know they inflate the numbers a little but guys in the know that have been in my car say that its pretty close so I would have to say alittle of verified and alittle estimated.

02-23-2013 10:18 AM

smith9300

Yea the cam I have now goes to 5200

02-23-2013 09:16 AM

vinniekq2

horse power

Quote:

Originally Posted by jtz55

are u running headers or stock exhaust .I have and am currently running a similar setup 485 lift cam 5.7 rods .it is putting out alittle over 400 hp and 525 ft lbs very good street manors .have fun with your 400 they make tremendous off idle torque and will shred the belts off most street tires.

varified or estimated?

the 400 came with 265 hp plus or minus
using a decent upgrade in cam/manifold/carb/headers could net 50 plus hp
vortec heads are very good improvement over most heads,especially for moderate performance and low lift cams.
vortecs flow 230 plus CFM on the intake side
these heads would peak at 5500 rpm on a 400.the cam would need to be big enough to rev 5500 to take full advantage of these heads

may need exhaust port worlk

02-23-2013 09:03 AM

smith9300

Headers for sure but it going in an 85 2500 with 6 in lift andon 33 but what is the complete build u have would like to compare

02-23-2013 08:12 AM

jtz55

are u running headers or stock exhaust .I have and am currently running a similar setup 485 lift cam 5.7 rods .it is putting out alittle over 400 hp and 525 ft lbs very good street manors .have fun with your 400 they make tremendous off idle torque and will shred the belts off most street tires.

02-23-2013 03:21 AM

smith9300

That seems pretty high to me with stock bottom end and just some new heads

02-22-2013 11:39 PM

JohnMatt

My guess is 420hp 450tq maybe more torque but those are my guesses

02-21-2013 11:58 AM

vinniekq2

vortec heads are limited to mid 400s plus or minus.If you use a hydraulic flat tappet look closer to 400. You can use a 750 cfm carb of bigger,depending on application.You will have good low RPM torque with those heads

02-21-2013 11:52 AM

smith9300

400 sbc hp?

hey guys just seeing if i can kind get a rough estimate on hp/tq on the engine i am going to be building